Conformationally Constrained Purine Mimics. Incorporation of Adenine and Guanine into Spirocyclic Nucleosides
作者:Leo A. Paquette、Alexandra L. Kahane、Christopher K. Seekamp
DOI:10.1021/jo049413z
日期:2004.8.1
Directed syntheses of spirocyclic nucleosides featuring adenine and guanine as the nucleobases have been successfully developed. The key starting materials are the enantiomerically pure spiro lactones 4, 15, and 28, which have proven amenable to conversion to anomeric mixtures of chloro sugars. The latter can enter into glycosidation by SN2 displacement with the sodium salts of 6-chloropurine or 2
已经成功开发了以腺嘌呤和鸟嘌呤为核碱基的螺环核苷的定向合成方法。的关键原料是对映体纯的螺内酯4,15,和28,这已被证明适合于转化为氯糖的端基异构体的混合物。后者可以通过6-N-嘌呤或2-氨基-6-氯嘌呤的钠盐通过S N 2置换而进入糖苷化反应。在饱和系列中,可以从19色谱分离出18。在涉及33和34的情况下,它们相对快速的差向异构化速度阻止了这种情况。模仿35 -37抗分离作为纯异头物。配置分配基于热互转换并支持MM3空间能量计算。从8的晶体学分析获得了更多的证实。尽管在所有晚期鸟嘌呤中间体中去除TBS保护基都是有问题的,但可以通过适当地利用四氧化钌氧化36来引入37中的一对羟基。